California Cities Ranked by Indoor Radon Levels

Measured averages from Airthings devices across California, USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.

Lake Arrowhead has the highest measured indoor radon in California at 7.0 pCi/L, based on Airthings measurements across 373 cities.

Updated September 28, 2026

Highest city

7.0pCi/L

Lake Arrowhead

California city average

1.0pCi/L

across 373 cities

Above action level

5/ 373

cities

California Cities Ranked by Indoor Radon Levels
#	Location	Avg level	vs action level
1	Lake Arrowhead	7.0 pCi/L	1.8× over
2	Mammoth Lakes	6.1 pCi/L	1.5× over
3	Deer Park	5.9 pCi/L	1.5× over
4	Echo Park	5.6 pCi/L	1.4× over
5	Alta Sierra	4.1 pCi/L	1.0× over
✓ Below EPA action level (4 pCi/L)
6	Atascadero	3.7 pCi/L	0.9× under
7	South Lake Tahoe	3.5 pCi/L	0.9× under
8	West Hills	3.5 pCi/L	0.9× under
9	Pomona	3.3 pCi/L	0.8× under
10	Fairfield	3.1 pCi/L	0.8× under
11	Brea	3.1 pCi/L	0.8× under
12	Mission Canyon	3.0 pCi/L	0.8× under
13	La Habra Heights	3.0 pCi/L	0.7× under
14	East Palo Alto	2.9 pCi/L	0.7× under
15	Alameda	2.8 pCi/L	0.7× under
16	Grass Valley	2.8 pCi/L	0.7× under
17	Truckee	2.8 pCi/L	0.7× under
18	Palos Verdes Estates	2.7 pCi/L	0.7× under
19	Oildale	2.6 pCi/L	0.7× under
20	Woodland Hills	2.6 pCi/L	0.7× under
21	Sunnyside-Tahoe City	2.6 pCi/L	0.7× under
22	Dollar Point	2.5 pCi/L	0.6× under
23	Nevada City	2.5 pCi/L	0.6× under
24	East Oakdale	2.5 pCi/L	0.6× under
25	Kings Beach	2.5 pCi/L	0.6× under
26	Hayward	2.4 pCi/L	0.6× under
27	Los Gatos	2.3 pCi/L	0.6× under
28	Twain Harte	2.3 pCi/L	0.6× under
29	Lexington Hills	2.3 pCi/L	0.6× under
30	Calabasas	2.2 pCi/L	0.6× under
31	Tahoe Vista	2.2 pCi/L	0.6× under
32	Hidden Hills	2.2 pCi/L	0.6× under
33	Lathrop	2.2 pCi/L	0.6× under
34	Rancho Palos Verdes	2.2 pCi/L	0.6× under
35	Portola Valley	2.1 pCi/L	0.5× under
36	Scotts Valley	2.1 pCi/L	0.5× under
37	Westlake Village	2.1 pCi/L	0.5× under
38	Felton	2.1 pCi/L	0.5× under
39	Tahoma	2.1 pCi/L	0.5× under
40	Minkler	2.1 pCi/L	0.5× under
41	Sherman Oaks	2.1 pCi/L	0.5× under
42	Fresno	2.1 pCi/L	0.5× under
43	Simi Valley	2.0 pCi/L	0.5× under
44	Montecito	2.0 pCi/L	0.5× under
45	Arnold	2.0 pCi/L	0.5× under
46	Boulder Creek	2.0 pCi/L	0.5× under
47	Agoura	1.9 pCi/L	0.5× under
48	Saratoga	1.9 pCi/L	0.5× under
49	Woodside	1.8 pCi/L	0.5× under
50	Pasatiempo	1.8 pCi/L	0.5× under
51	Ramona	1.8 pCi/L	0.5× under
52	Villa Park	1.8 pCi/L	0.5× under
53	Summerland	1.8 pCi/L	0.4× under
54	North Fair Oaks	1.7 pCi/L	0.4× under
55	Ojai	1.7 pCi/L	0.4× under
56	Isla Vista	1.7 pCi/L	0.4× under
57	Loyola	1.7 pCi/L	0.4× under
58	San Pedro	1.7 pCi/L	0.4× under
59	La Habra	1.6 pCi/L	0.4× under
60	Santa Susana	1.6 pCi/L	0.4× under
61	Northridge	1.6 pCi/L	0.4× under
62	Universal City	1.6 pCi/L	0.4× under
63	Fair Oaks	1.6 pCi/L	0.4× under
64	Modesto	1.5 pCi/L	0.4× under
65	Menlo Park	1.5 pCi/L	0.4× under
66	Laguna	1.5 pCi/L	0.4× under
67	Chico	1.5 pCi/L	0.4× under
68	Emeryville	1.5 pCi/L	0.4× under
69	Orinda	1.5 pCi/L	0.4× under
70	Buena Vista	1.5 pCi/L	0.4× under
71	Palm Springs	1.5 pCi/L	0.4× under
72	Palo Alto	1.5 pCi/L	0.4× under
73	Alturas	1.4 pCi/L	0.4× under
74	Culver City	1.4 pCi/L	0.4× under
75	Santa Barbara	1.4 pCi/L	0.4× under
76	Parkway	1.4 pCi/L	0.4× under
77	Alamo	1.4 pCi/L	0.4× under
78	East Richmond Heights	1.4 pCi/L	0.3× under
79	Corona	1.4 pCi/L	0.3× under
80	Rolling Hills Estates	1.3 pCi/L	0.3× under
81	Indio	1.3 pCi/L	0.3× under
82	Agoura Hills	1.3 pCi/L	0.3× under
83	Malibu Beach	1.3 pCi/L	0.3× under
84	Mount Hermon	1.3 pCi/L	0.3× under
85	Sleepy Hollow	1.3 pCi/L	0.3× under
86	Mission Viejo	1.3 pCi/L	0.3× under
87	Sunnyvale	1.3 pCi/L	0.3× under
88	Canoga Park	1.3 pCi/L	0.3× under
89	Davis	1.3 pCi/L	0.3× under
90	Fullerton	1.3 pCi/L	0.3× under
91	Brentwood	1.3 pCi/L	0.3× under
92	Atherton	1.3 pCi/L	0.3× under
93	Chino Hills	1.2 pCi/L	0.3× under
94	East Foothills	1.2 pCi/L	0.3× under
95	Empire	1.2 pCi/L	0.3× under
96	Gold River	1.2 pCi/L	0.3× under
97	North Hollywood	1.2 pCi/L	0.3× under
98	Visalia	1.2 pCi/L	0.3× under
99	Los Altos Hills	1.2 pCi/L	0.3× under
100	Placentia	1.2 pCi/L	0.3× under
101	Pleasant Hill	1.2 pCi/L	0.3× under
102	Campbell	1.2 pCi/L	0.3× under
103	Monterey Park	1.2 pCi/L	0.3× under
104	Vineyard	1.2 pCi/L	0.3× under
105	Los Altos	1.1 pCi/L	0.3× under
106	Piedmont	1.1 pCi/L	0.3× under
107	Newark	1.1 pCi/L	0.3× under
108	Altadena	1.1 pCi/L	0.3× under
109	Anaheim	1.1 pCi/L	0.3× under
110	Rolling Hills	1.1 pCi/L	0.3× under
111	Poway	1.1 pCi/L	0.3× under
112	Concord	1.1 pCi/L	0.3× under
113	Glendale	1.1 pCi/L	0.3× under
114	Carmel Valley Village	1.1 pCi/L	0.3× under
115	Lincoln Village	1.1 pCi/L	0.3× under
116	Redwood City	1.1 pCi/L	0.3× under
117	Oceanside	1.1 pCi/L	0.3× under
118	Salinas	1.1 pCi/L	0.3× under
119	Corte Madera	1.0 pCi/L	0.3× under
120	Goleta	1.0 pCi/L	0.3× under
121	Malibu	1.0 pCi/L	0.3× under
122	Topanga	1.0 pCi/L	0.3× under
123	Castro Valley	1.0 pCi/L	0.3× under
124	West Menlo Park	1.0 pCi/L	0.3× under
125	East Pasadena	1.0 pCi/L	0.3× under
126	Carmel-by-the-Sea	1.0 pCi/L	0.3× under
127	Danville	1.0 pCi/L	0.3× under
128	Kensington	1.0 pCi/L	0.3× under
129	Hacienda Heights	1.0 pCi/L	0.3× under
130	Orangevale	1.0 pCi/L	0.3× under
131	Van Nuys	1.0 pCi/L	0.3× under
132	Casa de Oro-Mount Helix	1.0 pCi/L	0.2× under
133	Santa Clara	1.0 pCi/L	0.2× under
134	Los Serranos	1.0 pCi/L	0.2× under
135	Walnut	1.0 pCi/L	0.2× under
136	Clovis	0.9 pCi/L	0.2× under
137	Cupertino	0.9 pCi/L	0.2× under
138	Hollywood	0.9 pCi/L	0.2× under
139	Yountville	0.9 pCi/L	0.2× under
140	Emerald Lake Hills	0.9 pCi/L	0.2× under
141	Belvedere	0.9 pCi/L	0.2× under
142	Oak Park	0.9 pCi/L	0.2× under
143	Chatsworth	0.9 pCi/L	0.2× under
144	Ladera	0.9 pCi/L	0.2× under
145	Santa Monica	0.9 pCi/L	0.2× under
146	Santa Venetia	0.9 pCi/L	0.2× under
147	Walnut Creek	0.9 pCi/L	0.2× under
148	Whittier	0.9 pCi/L	0.2× under
149	Century City	0.9 pCi/L	0.2× under
150	Home Gardens	0.9 pCi/L	0.2× under
151	San Luis Obispo	0.9 pCi/L	0.2× under
152	South Pasadena	0.9 pCi/L	0.2× under
153	Sacramento	0.9 pCi/L	0.2× under
154	Tustin	0.9 pCi/L	0.2× under
155	Ventura	0.9 pCi/L	0.2× under
156	Westwood, Los Angeles	0.9 pCi/L	0.2× under
157	Tracy	0.9 pCi/L	0.2× under
158	Monte Sereno	0.9 pCi/L	0.2× under
159	Woodland	0.9 pCi/L	0.2× under
160	Belmont	0.8 pCi/L	0.2× under
161	Moraga	0.8 pCi/L	0.2× under
162	Mountain View	0.8 pCi/L	0.2× under
163	San Juan Capistrano	0.8 pCi/L	0.2× under
164	La Verne	0.8 pCi/L	0.2× under
165	San Marino	0.8 pCi/L	0.2× under
166	Camarillo	0.8 pCi/L	0.2× under
167	Highlands-Baywood Park	0.8 pCi/L	0.2× under
168	Novato	0.8 pCi/L	0.2× under
169	Saranap	0.8 pCi/L	0.2× under
170	Cambrian Park	0.8 pCi/L	0.2× under
171	Elk Grove	0.8 pCi/L	0.2× under
172	Yorba Linda	0.8 pCi/L	0.2× under
173	Diamond Bar	0.8 pCi/L	0.2× under
174	Fairbanks Ranch	0.8 pCi/L	0.2× under
175	Silver Lake	0.8 pCi/L	0.2× under
176	Thousand Oaks	0.8 pCi/L	0.2× under
177	Fairfax	0.8 pCi/L	0.2× under
178	Fremont	0.8 pCi/L	0.2× under
179	San Anselmo	0.8 pCi/L	0.2× under
180	Beverly Hills	0.8 pCi/L	0.2× under
181	Fairview	0.8 pCi/L	0.2× under
182	Fontana	0.8 pCi/L	0.2× under
183	Sausalito	0.8 pCi/L	0.2× under
184	Bonsall	0.8 pCi/L	0.2× under
185	Carmichael	0.8 pCi/L	0.2× under
186	Laguna Woods	0.8 pCi/L	0.2× under
187	Folsom	0.8 pCi/L	0.2× under
188	Lafayette	0.8 pCi/L	0.2× under
189	Seven Trees	0.8 pCi/L	0.2× under
190	Moorpark	0.8 pCi/L	0.2× under
191	Murrieta Hot Springs	0.8 pCi/L	0.2× under
192	Rancho Santa Fe	0.8 pCi/L	0.2× under
193	El Cerrito	0.7 pCi/L	0.2× under
194	La Crescenta-Montrose	0.7 pCi/L	0.2× under
195	Albany	0.7 pCi/L	0.2× under
196	Gilroy	0.7 pCi/L	0.2× under
197	Los Angeles	0.7 pCi/L	0.2× under
198	Redlands	0.7 pCi/L	0.2× under
199	Stanford	0.7 pCi/L	0.2× under
200	Union City	0.7 pCi/L	0.2× under
201	Berkeley	0.7 pCi/L	0.2× under
202	Brisbane	0.7 pCi/L	0.2× under
203	Lomita	0.7 pCi/L	0.2× under
204	Marina del Rey	0.7 pCi/L	0.2× under
205	Pasadena	0.7 pCi/L	0.2× under
206	Roseville	0.7 pCi/L	0.2× under
207	San Carlos	0.7 pCi/L	0.2× under
208	Westminster	0.7 pCi/L	0.2× under
209	Burlingame	0.7 pCi/L	0.2× under
210	Rocklin	0.7 pCi/L	0.2× under
211	San Leandro	0.7 pCi/L	0.2× under
212	Mill Valley	0.7 pCi/L	0.2× under
213	Oxnard	0.7 pCi/L	0.2× under
214	Rowland Heights	0.7 pCi/L	0.2× under
215	San Fernando	0.7 pCi/L	0.2× under
216	Sebastopol	0.7 pCi/L	0.2× under
217	Waldon	0.7 pCi/L	0.2× under
218	Benicia	0.7 pCi/L	0.2× under
219	Burbank	0.7 pCi/L	0.2× under
220	San Gabriel	0.7 pCi/L	0.2× under
221	Sonoma	0.7 pCi/L	0.2× under
222	El Sobrante	0.7 pCi/L	0.2× under
223	Las Flores	0.7 pCi/L	0.2× under
224	Rancho Mirage	0.7 pCi/L	0.2× under
225	Alum Rock	0.7 pCi/L	0.2× under
226	Del Mar	0.7 pCi/L	0.2× under
227	East San Gabriel	0.7 pCi/L	0.2× under
228	Hermosa Beach	0.7 pCi/L	0.2× under
229	San Marcos	0.7 pCi/L	0.2× under
230	Santa Ana	0.7 pCi/L	0.2× under
231	Alondra Park	0.7 pCi/L	0.2× under
232	Aptos	0.7 pCi/L	0.2× under
233	Clayton	0.7 pCi/L	0.2× under
234	Escondido	0.7 pCi/L	0.2× under
235	Ladera Heights	0.7 pCi/L	0.2× under
236	Ladera Ranch	0.7 pCi/L	0.2× under
237	Lucas Valley-Marinwood	0.7 pCi/L	0.2× under
238	San Joaquin Hills	0.7 pCi/L	0.2× under
239	Valley Center	0.7 pCi/L	0.2× under
240	Morongo Valley	0.6 pCi/L	0.2× under
241	Del Aire	0.6 pCi/L	0.2× under
242	Inglewood	0.6 pCi/L	0.2× under
243	La Mesa	0.6 pCi/L	0.2× under
244	Woodcrest	0.6 pCi/L	0.2× under
245	Carlsbad	0.6 pCi/L	0.2× under
246	Morgan Hill	0.6 pCi/L	0.2× under
247	North Tustin	0.6 pCi/L	0.2× under
248	Oxnard Shores	0.6 pCi/L	0.2× under
249	San Rafael	0.6 pCi/L	0.2× under
250	Livermore	0.6 pCi/L	0.2× under
251	San Jose	0.6 pCi/L	0.2× under
252	San Ramon	0.6 pCi/L	0.2× under
253	Alhambra	0.6 pCi/L	0.1× under
254	El Granada	0.6 pCi/L	0.1× under
255	La Jolla	0.6 pCi/L	0.1× under
256	Lincoln	0.6 pCi/L	0.1× under
257	Portola Hills	0.6 pCi/L	0.1× under
258	Saticoy	0.6 pCi/L	0.1× under
259	View Park-Windsor Hills	0.6 pCi/L	0.1× under
260	West Hollywood	0.6 pCi/L	0.1× under
261	Buena Park	0.6 pCi/L	0.1× under
262	Daly City	0.6 pCi/L	0.1× under
263	La Canada Flintridge	0.6 pCi/L	0.1× under
264	Laguna Beach	0.6 pCi/L	0.1× under
265	Cerritos	0.6 pCi/L	0.1× under
266	Indian Wells	0.6 pCi/L	0.1× under
267	Milpitas	0.6 pCi/L	0.1× under
268	San Diego	0.6 pCi/L	0.1× under
269	Santa Cruz	0.6 pCi/L	0.1× under
270	West Sacramento	0.6 pCi/L	0.1× under
271	El Cajon	0.6 pCi/L	0.1× under
272	Laguna Niguel	0.6 pCi/L	0.1× under
273	Temple City	0.6 pCi/L	0.1× under
274	Vallejo	0.6 pCi/L	0.1× under
275	Foothill Ranch	0.6 pCi/L	0.1× under
276	Hillsborough	0.6 pCi/L	0.1× under
277	San Mateo	0.6 pCi/L	0.1× under
278	Stanton	0.6 pCi/L	0.1× under
279	Antelope	0.6 pCi/L	0.1× under
280	Bakersfield	0.6 pCi/L	0.1× under
281	San Clemente	0.5 pCi/L	0.1× under
282	Lake San Marcos	0.5 pCi/L	0.1× under
283	Pleasanton	0.5 pCi/L	0.1× under
284	Blackhawk	0.5 pCi/L	0.1× under
285	Fallbrook	0.5 pCi/L	0.1× under
286	Irvine	0.5 pCi/L	0.1× under
287	Lake Forest	0.5 pCi/L	0.1× under
288	Rossmoor	0.5 pCi/L	0.1× under
289	Trabuco Canyon	0.5 pCi/L	0.1× under
290	Boyle Heights	0.5 pCi/L	0.1× under
291	Dublin	0.5 pCi/L	0.1× under
292	Encinitas	0.5 pCi/L	0.1× under
293	Napa	0.5 pCi/L	0.1× under
294	Vacaville	0.5 pCi/L	0.1× under
295	East La Mirada	0.5 pCi/L	0.1× under
296	Oakland	0.5 pCi/L	0.1× under
297	San Francisco	0.5 pCi/L	0.1× under
298	Ashland	0.5 pCi/L	0.1× under
299	El Rio	0.5 pCi/L	0.1× under
300	Larkfield-Wikiup	0.5 pCi/L	0.1× under
301	Monrovia	0.5 pCi/L	0.1× under
302	Tamalpais-Homestead Valley	0.5 pCi/L	0.1× under
303	El Dorado Hills	0.5 pCi/L	0.1× under
304	Richmond	0.5 pCi/L	0.1× under
305	San Antonio Heights	0.5 pCi/L	0.1× under
306	Aliso Viejo	0.5 pCi/L	0.1× under
307	Healdsburg	0.5 pCi/L	0.1× under
308	Mira Loma	0.5 pCi/L	0.1× under
309	Torrance	0.5 pCi/L	0.1× under
310	Colma	0.5 pCi/L	0.1× under
311	Redondo Beach	0.5 pCi/L	0.1× under
312	Sierra Madre	0.5 pCi/L	0.1× under
313	Windsor	0.5 pCi/L	0.1× under
314	Cameron Park	0.4 pCi/L	0.1× under
315	Del Rey Oaks	0.4 pCi/L	0.1× under
316	Los Alamitos	0.4 pCi/L	0.1× under
317	Rancho Cucamonga	0.4 pCi/L	0.1× under
318	Santa Rosa	0.4 pCi/L	0.1× under
319	Strawberry	0.4 pCi/L	0.1× under
320	Casa Conejo	0.4 pCi/L	0.1× under
321	Huntington Beach	0.4 pCi/L	0.1× under
322	Orcutt	0.4 pCi/L	0.1× under
323	Lemon Grove	0.4 pCi/L	0.1× under
324	Vista	0.4 pCi/L	0.1× under
325	Claremont	0.4 pCi/L	0.1× under
326	Coronado	0.4 pCi/L	0.1× under
327	Gardena	0.4 pCi/L	0.1× under
328	Midway City	0.4 pCi/L	0.1× under
329	Montebello	0.4 pCi/L	0.1× under
330	Arden-Arcade	0.4 pCi/L	0.1× under
331	Chino	0.4 pCi/L	0.1× under
332	El Segundo	0.4 pCi/L	0.1× under
333	Guerneville	0.4 pCi/L	0.1× under
334	Mayflower Village	0.4 pCi/L	0.1× under
335	Santa Clarita	0.4 pCi/L	0.1× under
336	Temecula	0.4 pCi/L	0.1× under
337	Costa Mesa	0.4 pCi/L	0.1× under
338	Fountain Valley	0.4 pCi/L	0.1× under
339	Redwood Shores	0.4 pCi/L	0.1× under
340	Seacliff	0.4 pCi/L	0.1× under
341	Manhattan Beach	0.4 pCi/L	0.1× under
342	La Mirada	0.3 pCi/L	0.1× under
343	Norco	0.3 pCi/L	0.1× under
344	North Glendale	0.3 pCi/L	0.1× under
345	Pacifica	0.3 pCi/L	0.1× under
346	Hawaiian Gardens	0.3 pCi/L	0.1× under
347	Millbrae	0.3 pCi/L	0.1× under
348	National City	0.3 pCi/L	0.1× under
349	Yucaipa	0.3 pCi/L	0.1× under
350	Granite Bay	0.3 pCi/L	0.1× under
351	Lakewood	0.3 pCi/L	0.1× under
352	Long Beach	0.3 pCi/L	0.1× under
353	Orange	0.3 pCi/L	0.1× under
354	Palm Desert	0.3 pCi/L	0.1× under
355	Signal Hill	0.3 pCi/L	0.1× under
356	La Palma	0.3 pCi/L	0.1× under
357	South San Francisco	0.3 pCi/L	0.1× under
358	Valencia	0.3 pCi/L	0.1× under
359	Lawndale	0.3 pCi/L	0.1× under
360	Pacific Grove	0.3 pCi/L	0.1× under
361	Petaluma	0.3 pCi/L	0.1× under
362	Arcadia	0.3 pCi/L	0.1× under
363	Cypress	0.3 pCi/L	0.1× under
364	Opal Cliffs	0.3 pCi/L	0.1× under
365	Lompoc	0.3 pCi/L	0.1× under
366	Bonita	0.3 pCi/L	0.1× under
367	Broadmoor	0.3 pCi/L	0.1× under
368	Newport Beach	0.3 pCi/L	0.1× under
369	Seal Beach	0.2 pCi/L	0.1× under
370	Foster City	0.2 pCi/L	0.1× under
371	Santa Fe Springs	0.2 pCi/L	0.1× under
372	San Lorenzo	0.2 pCi/L	0.1× under
373	Norwalk	0.1 pCi/L	0.0× under

See USA cities ranked by radon level See all States ranked by radon level