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 7.6 pCi/L, based on Airthings measurements across 338 cities.

Updated August 16, 2026

Highest city

7.6pCi/L

Lake Arrowhead

California city average

1.1pCi/L

across 338 cities

Above action level

5/ 338

cities

California Cities Ranked by Indoor Radon Levels
#	Location	Avg level	Monitors	vs action level
1	Lake Arrowhead	7.6 pCi/L	6	1.9× over
2	Mammoth Lakes	6.3 pCi/L	11	1.6× over
3	Deer Park	5.9 pCi/L	8	1.5× over
4	Echo Park	5.6 pCi/L	96	1.4× over
5	Alta Sierra	4.6 pCi/L	7	1.2× over
✓ Below EPA action level (4 pCi/L)
6	South Lake Tahoe	3.5 pCi/L	89	0.9× under
7	Pomona	3.5 pCi/L	11	0.9× under
8	West Hills	3.5 pCi/L	21	0.9× under
9	Fairfield	3.1 pCi/L	8	0.8× under
10	Mission Canyon	3.1 pCi/L	27	0.8× under
11	Brea	3.1 pCi/L	7	0.8× under
12	La Habra Heights	3.0 pCi/L	7	0.7× under
13	East Palo Alto	2.9 pCi/L	33	0.7× under
14	Alameda	2.8 pCi/L	159	0.7× under
15	Truckee	2.8 pCi/L	96	0.7× under
16	Grass Valley	2.8 pCi/L	8	0.7× under
17	Palos Verdes Estates	2.8 pCi/L	59	0.7× under
18	Woodland Hills	2.7 pCi/L	54	0.7× under
19	Oildale	2.6 pCi/L	9	0.7× under
20	Sunnyside-Tahoe City	2.6 pCi/L	16	0.7× under
21	Nevada City	2.5 pCi/L	14	0.6× under
22	Hayward	2.4 pCi/L	92	0.6× under
23	Los Gatos	2.3 pCi/L	34	0.6× under
24	Lexington Hills	2.3 pCi/L	31	0.6× under
25	Portola Valley	2.2 pCi/L	14	0.6× under
26	Calabasas	2.2 pCi/L	13	0.6× under
27	Kings Beach	2.2 pCi/L	16	0.6× under
28	Tahoe Vista	2.2 pCi/L	15	0.6× under
29	Hidden Hills	2.2 pCi/L	20	0.6× under
30	Lathrop	2.2 pCi/L	8	0.6× under
31	Rancho Palos Verdes	2.2 pCi/L	30	0.6× under
32	Scotts Valley	2.1 pCi/L	14	0.5× under
33	Sherman Oaks	2.1 pCi/L	128	0.5× under
34	Westlake Village	2.1 pCi/L	6	0.5× under
35	Tahoma	2.1 pCi/L	6	0.5× under
36	Minkler	2.1 pCi/L	6	0.5× under
37	Fresno	2.1 pCi/L	10	0.5× under
38	Simi Valley	2.0 pCi/L	8	0.5× under
39	Montecito	2.0 pCi/L	16	0.5× under
40	Arnold	2.0 pCi/L	10	0.5× under
41	Boulder Creek	2.0 pCi/L	12	0.5× under
42	Agoura	1.9 pCi/L	7	0.5× under
43	Ramona	1.9 pCi/L	7	0.5× under
44	Saratoga	1.9 pCi/L	51	0.5× under
45	Woodside	1.8 pCi/L	20	0.5× under
46	Villa Park	1.8 pCi/L	33	0.5× under
47	Summerland	1.8 pCi/L	7	0.4× under
48	North Fair Oaks	1.7 pCi/L	10	0.4× under
49	Isla Vista	1.7 pCi/L	19	0.4× under
50	Loyola	1.7 pCi/L	33	0.4× under
51	Ojai	1.7 pCi/L	12	0.4× under
52	Universal City	1.7 pCi/L	42	0.4× under
53	San Pedro	1.7 pCi/L	20	0.4× under
54	La Habra	1.6 pCi/L	13	0.4× under
55	Northridge	1.6 pCi/L	76	0.4× under
56	Santa Susana	1.6 pCi/L	8	0.4× under
57	Fair Oaks	1.6 pCi/L	9	0.4× under
58	Menlo Park	1.6 pCi/L	51	0.4× under
59	Modesto	1.5 pCi/L	7	0.4× under
60	Laguna	1.5 pCi/L	15	0.4× under
61	Culver City	1.5 pCi/L	57	0.4× under
62	Emeryville	1.5 pCi/L	93	0.4× under
63	Palo Alto	1.5 pCi/L	109	0.4× under
64	Buena Vista	1.5 pCi/L	68	0.4× under
65	Chico	1.5 pCi/L	10	0.4× under
66	Orinda	1.5 pCi/L	31	0.4× under
67	East Richmond Heights	1.4 pCi/L	8	0.4× under
68	Palm Springs	1.4 pCi/L	8	0.4× under
69	Parkway	1.4 pCi/L	7	0.4× under
70	Santa Barbara	1.4 pCi/L	63	0.4× under
71	Alamo	1.4 pCi/L	13	0.4× under
72	Corona	1.4 pCi/L	9	0.3× under
73	Rolling Hills Estates	1.3 pCi/L	42	0.3× under
74	Agoura Hills	1.3 pCi/L	10	0.3× under
75	Malibu Beach	1.3 pCi/L	17	0.3× under
76	Mount Hermon	1.3 pCi/L	10	0.3× under
77	Sleepy Hollow	1.3 pCi/L	11	0.3× under
78	Mission Viejo	1.3 pCi/L	17	0.3× under
79	Sunnyvale	1.3 pCi/L	179	0.3× under
80	Visalia	1.3 pCi/L	9	0.3× under
81	Davis	1.3 pCi/L	22	0.3× under
82	Fullerton	1.3 pCi/L	14	0.3× under
83	Brentwood	1.3 pCi/L	14	0.3× under
84	Atherton	1.3 pCi/L	19	0.3× under
85	Canoga Park	1.2 pCi/L	19	0.3× under
86	Chino Hills	1.2 pCi/L	16	0.3× under
87	East Foothills	1.2 pCi/L	7	0.3× under
88	Empire	1.2 pCi/L	6	0.3× under
89	Gold River	1.2 pCi/L	6	0.3× under
90	Pleasant Hill	1.2 pCi/L	11	0.3× under
91	Los Altos Hills	1.2 pCi/L	52	0.3× under
92	North Hollywood	1.2 pCi/L	64	0.3× under
93	Placentia	1.2 pCi/L	9	0.3× under
94	Monterey Park	1.2 pCi/L	19	0.3× under
95	Campbell	1.2 pCi/L	60	0.3× under
96	Los Altos	1.2 pCi/L	62	0.3× under
97	Piedmont	1.2 pCi/L	100	0.3× under
98	Vineyard	1.2 pCi/L	8	0.3× under
99	Carmel Valley Village	1.1 pCi/L	10	0.3× under
100	Newark	1.1 pCi/L	55	0.3× under
101	Altadena	1.1 pCi/L	93	0.3× under
102	Rolling Hills	1.1 pCi/L	12	0.3× under
103	Anaheim	1.1 pCi/L	6	0.3× under
104	Concord	1.1 pCi/L	24	0.3× under
105	Redwood City	1.1 pCi/L	45	0.3× under
106	West Menlo Park	1.1 pCi/L	37	0.3× under
107	Glendale	1.1 pCi/L	71	0.3× under
108	Kensington	1.1 pCi/L	11	0.3× under
109	Lincoln Village	1.1 pCi/L	6	0.3× under
110	Oceanside	1.1 pCi/L	6	0.3× under
111	Castro Valley	1.0 pCi/L	25	0.3× under
112	Corte Madera	1.0 pCi/L	9	0.3× under
113	Goleta	1.0 pCi/L	25	0.3× under
114	Malibu	1.0 pCi/L	10	0.3× under
115	Topanga	1.0 pCi/L	34	0.3× under
116	East Pasadena	1.0 pCi/L	50	0.3× under
117	Poway	1.0 pCi/L	54	0.3× under
118	Van Nuys	1.0 pCi/L	22	0.3× under
119	Carmel-by-the-Sea	1.0 pCi/L	18	0.3× under
120	Danville	1.0 pCi/L	23	0.3× under
121	Santa Clara	1.0 pCi/L	102	0.3× under
122	Hacienda Heights	1.0 pCi/L	9	0.3× under
123	Orangevale	1.0 pCi/L	9	0.3× under
124	Walnut	1.0 pCi/L	6	0.3× under
125	Belvedere	1.0 pCi/L	8	0.2× under
126	Cupertino	1.0 pCi/L	117	0.2× under
127	Los Serranos	1.0 pCi/L	8	0.2× under
128	Clovis	0.9 pCi/L	16	0.2× under
129	Elk Grove	0.9 pCi/L	6	0.2× under
130	Emerald Lake Hills	0.9 pCi/L	28	0.2× under
131	Oak Park	0.9 pCi/L	12	0.2× under
132	Hollywood	0.9 pCi/L	80	0.2× under
133	Yountville	0.9 pCi/L	6	0.2× under
134	South Pasadena	0.9 pCi/L	86	0.2× under
135	Walnut Creek	0.9 pCi/L	19	0.2× under
136	Century City	0.9 pCi/L	28	0.2× under
137	Chatsworth	0.9 pCi/L	22	0.2× under
138	Ladera	0.9 pCi/L	6	0.2× under
139	Santa Monica	0.9 pCi/L	218	0.2× under
140	Home Gardens	0.9 pCi/L	7	0.2× under
141	Sacramento	0.9 pCi/L	55	0.2× under
142	San Luis Obispo	0.9 pCi/L	19	0.2× under
143	Tustin	0.9 pCi/L	12	0.2× under
144	Ventura	0.9 pCi/L	16	0.2× under
145	Westwood, Los Angeles	0.9 pCi/L	88	0.2× under
146	Tracy	0.9 pCi/L	24	0.2× under
147	San Anselmo	0.9 pCi/L	6	0.2× under
148	San Marino	0.9 pCi/L	12	0.2× under
149	Woodland	0.9 pCi/L	6	0.2× under
150	Monte Sereno	0.8 pCi/L	17	0.2× under
151	Moraga	0.8 pCi/L	17	0.2× under
152	Mountain View	0.8 pCi/L	130	0.2× under
153	San Juan Capistrano	0.8 pCi/L	7	0.2× under
154	Cambrian Park	0.8 pCi/L	78	0.2× under
155	Highlands-Baywood Park	0.8 pCi/L	26	0.2× under
156	Camarillo	0.8 pCi/L	8	0.2× under
157	Novato	0.8 pCi/L	8	0.2× under
158	Saranap	0.8 pCi/L	8	0.2× under
159	Silver Lake	0.8 pCi/L	85	0.2× under
160	Yorba Linda	0.8 pCi/L	19	0.2× under
161	Diamond Bar	0.8 pCi/L	10	0.2× under
162	Fairbanks Ranch	0.8 pCi/L	58	0.2× under
163	Thousand Oaks	0.8 pCi/L	29	0.2× under
164	Beverly Hills	0.8 pCi/L	35	0.2× under
165	Burbank	0.8 pCi/L	43	0.2× under
166	Fontana	0.8 pCi/L	14	0.2× under
167	Fremont	0.8 pCi/L	80	0.2× under
168	Fairfax	0.8 pCi/L	11	0.2× under
169	Rancho Santa Fe	0.8 pCi/L	10	0.2× under
170	Fairview	0.8 pCi/L	24	0.2× under
171	Sausalito	0.8 pCi/L	8	0.2× under
172	Carmichael	0.8 pCi/L	15	0.2× under
173	Folsom	0.8 pCi/L	22	0.2× under
174	Lafayette	0.8 pCi/L	25	0.2× under
175	Seven Trees	0.8 pCi/L	94	0.2× under
176	Gilroy	0.8 pCi/L	7	0.2× under
177	Moorpark	0.8 pCi/L	12	0.2× under
178	Murrieta Hot Springs	0.8 pCi/L	8	0.2× under
179	Westminster	0.8 pCi/L	17	0.2× under
180	Belmont	0.7 pCi/L	77	0.2× under
181	El Cerrito	0.7 pCi/L	24	0.2× under
182	La Crescenta-Montrose	0.7 pCi/L	36	0.2× under
183	Los Angeles	0.7 pCi/L	83	0.2× under
184	Albany	0.7 pCi/L	31	0.2× under
185	Berkeley	0.7 pCi/L	107	0.2× under
186	Lomita	0.7 pCi/L	11	0.2× under
187	Redlands	0.7 pCi/L	12	0.2× under
188	Stanford	0.7 pCi/L	15	0.2× under
189	Union City	0.7 pCi/L	41	0.2× under
190	Rocklin	0.7 pCi/L	19	0.2× under
191	San Carlos	0.7 pCi/L	50	0.2× under
192	Brisbane	0.7 pCi/L	18	0.2× under
193	Burlingame	0.7 pCi/L	17	0.2× under
194	Marina del Rey	0.7 pCi/L	102	0.2× under
195	Pasadena	0.7 pCi/L	90	0.2× under
196	San Leandro	0.7 pCi/L	67	0.2× under
197	Rowland Heights	0.7 pCi/L	6	0.2× under
198	San Fernando	0.7 pCi/L	15	0.2× under
199	Benicia	0.7 pCi/L	6	0.2× under
200	San Gabriel	0.7 pCi/L	6	0.2× under
201	Sebastopol	0.7 pCi/L	9	0.2× under
202	Alum Rock	0.7 pCi/L	19	0.2× under
203	Del Mar	0.7 pCi/L	24	0.2× under
204	El Sobrante	0.7 pCi/L	10	0.2× under
205	Las Flores	0.7 pCi/L	13	0.2× under
206	Rancho Mirage	0.7 pCi/L	9	0.2× under
207	Clayton	0.7 pCi/L	9	0.2× under
208	Hermosa Beach	0.7 pCi/L	17	0.2× under
209	San Marcos	0.7 pCi/L	12	0.2× under
210	Santa Ana	0.7 pCi/L	15	0.2× under
211	Alondra Park	0.7 pCi/L	6	0.2× under
212	Aptos	0.7 pCi/L	6	0.2× under
213	Escondido	0.7 pCi/L	12	0.2× under
214	Ladera Heights	0.7 pCi/L	17	0.2× under
215	Ladera Ranch	0.7 pCi/L	25	0.2× under
216	Lucas Valley-Marinwood	0.7 pCi/L	12	0.2× under
217	San Joaquin Hills	0.7 pCi/L	30	0.2× under
218	Carlsbad	0.6 pCi/L	20	0.2× under
219	Morongo Valley	0.6 pCi/L	6	0.2× under
220	Del Aire	0.6 pCi/L	6	0.2× under
221	Inglewood	0.6 pCi/L	21	0.2× under
222	La Mesa	0.6 pCi/L	39	0.2× under
223	Laguna Beach	0.6 pCi/L	14	0.2× under
224	Morgan Hill	0.6 pCi/L	26	0.2× under
225	North Tustin	0.6 pCi/L	46	0.2× under
226	Woodcrest	0.6 pCi/L	7	0.2× under
227	Mill Valley	0.6 pCi/L	12	0.2× under
228	Oxnard Shores	0.6 pCi/L	7	0.2× under
229	San Rafael	0.6 pCi/L	10	0.2× under
230	San Ramon	0.6 pCi/L	67	0.2× under
231	San Jose	0.6 pCi/L	140	0.2× under
232	West Hollywood	0.6 pCi/L	78	0.2× under
233	Alhambra	0.6 pCi/L	12	0.1× under
234	El Granada	0.6 pCi/L	12	0.1× under
235	Lincoln	0.6 pCi/L	12	0.1× under
236	Livermore	0.6 pCi/L	37	0.1× under
237	Portola Hills	0.6 pCi/L	6	0.1× under
238	Saticoy	0.6 pCi/L	6	0.1× under
239	Daly City	0.6 pCi/L	104	0.1× under
240	La Canada Flintridge	0.6 pCi/L	28	0.1× under
241	La Jolla	0.6 pCi/L	56	0.1× under
242	Laguna Niguel	0.6 pCi/L	11	0.1× under
243	Laguna Woods	0.6 pCi/L	19	0.1× under
244	View Park-Windsor Hills	0.6 pCi/L	29	0.1× under
245	Cerritos	0.6 pCi/L	11	0.1× under
246	Milpitas	0.6 pCi/L	65	0.1× under
247	San Diego	0.6 pCi/L	100	0.1× under
248	Santa Cruz	0.6 pCi/L	21	0.1× under
249	West Sacramento	0.6 pCi/L	13	0.1× under
250	San Mateo	0.6 pCi/L	46	0.1× under
251	Temple City	0.6 pCi/L	16	0.1× under
252	Vallejo	0.6 pCi/L	8	0.1× under
253	Foothill Ranch	0.6 pCi/L	9	0.1× under
254	Hillsborough	0.6 pCi/L	28	0.1× under
255	Waldon	0.6 pCi/L	8	0.1× under
256	Antelope	0.6 pCi/L	15	0.1× under
257	Pleasanton	0.5 pCi/L	48	0.1× under
258	San Clemente	0.5 pCi/L	20	0.1× under
259	Blackhawk	0.5 pCi/L	20	0.1× under
260	Lake Forest	0.5 pCi/L	33	0.1× under
261	Aliso Viejo	0.5 pCi/L	15	0.1× under
262	Encinitas	0.5 pCi/L	22	0.1× under
263	Rossmoor	0.5 pCi/L	9	0.1× under
264	Trabuco Canyon	0.5 pCi/L	6	0.1× under
265	Boyle Heights	0.5 pCi/L	7	0.1× under
266	Dublin	0.5 pCi/L	22	0.1× under
267	Irvine	0.5 pCi/L	75	0.1× under
268	Lake San Marcos	0.5 pCi/L	11	0.1× under
269	Napa	0.5 pCi/L	11	0.1× under
270	Vacaville	0.5 pCi/L	6	0.1× under
271	East La Mirada	0.5 pCi/L	6	0.1× under
272	Oakland	0.5 pCi/L	103	0.1× under
273	Ashland	0.5 pCi/L	7	0.1× under
274	Monrovia	0.5 pCi/L	10	0.1× under
275	San Francisco	0.5 pCi/L	602	0.1× under
276	Tamalpais-Homestead Valley	0.5 pCi/L	8	0.1× under
277	El Dorado Hills	0.5 pCi/L	29	0.1× under
278	Larkfield-Wikiup	0.5 pCi/L	6	0.1× under
279	Richmond	0.5 pCi/L	11	0.1× under
280	San Antonio Heights	0.5 pCi/L	12	0.1× under
281	Healdsburg	0.5 pCi/L	6	0.1× under
282	Mira Loma	0.5 pCi/L	8	0.1× under
283	Torrance	0.5 pCi/L	24	0.1× under
284	Colma	0.5 pCi/L	15	0.1× under
285	Huntington Beach	0.5 pCi/L	12	0.1× under
286	Redondo Beach	0.5 pCi/L	29	0.1× under
287	Sierra Madre	0.5 pCi/L	20	0.1× under
288	Windsor	0.5 pCi/L	10	0.1× under
289	Del Rey Oaks	0.4 pCi/L	6	0.1× under
290	Los Alamitos	0.4 pCi/L	8	0.1× under
291	Rancho Cucamonga	0.4 pCi/L	16	0.1× under
292	Santa Rosa	0.4 pCi/L	12	0.1× under
293	Strawberry	0.4 pCi/L	20	0.1× under
294	Casa Conejo	0.4 pCi/L	15	0.1× under
295	Buena Park	0.4 pCi/L	8	0.1× under
296	Lemon Grove	0.4 pCi/L	7	0.1× under
297	Vista	0.4 pCi/L	29	0.1× under
298	Claremont	0.4 pCi/L	9	0.1× under
299	Gardena	0.4 pCi/L	8	0.1× under
300	Arden-Arcade	0.4 pCi/L	13	0.1× under
301	Chino	0.4 pCi/L	8	0.1× under
302	Costa Mesa	0.4 pCi/L	17	0.1× under
303	El Segundo	0.4 pCi/L	7	0.1× under
304	Santa Clarita	0.4 pCi/L	23	0.1× under
305	Coronado	0.4 pCi/L	13	0.1× under
306	Temecula	0.4 pCi/L	13	0.1× under
307	Fountain Valley	0.4 pCi/L	13	0.1× under
308	Seacliff	0.4 pCi/L	9	0.1× under
309	Midway City	0.4 pCi/L	8	0.1× under
310	Pacifica	0.4 pCi/L	10	0.1× under
311	Redwood Shores	0.4 pCi/L	20	0.1× under
312	La Mirada	0.3 pCi/L	6	0.1× under
313	Manhattan Beach	0.3 pCi/L	29	0.1× under
314	National City	0.3 pCi/L	11	0.1× under
315	Norco	0.3 pCi/L	6	0.1× under
316	Hawaiian Gardens	0.3 pCi/L	9	0.1× under
317	Millbrae	0.3 pCi/L	25	0.1× under
318	Long Beach	0.3 pCi/L	19	0.1× under
319	Lakewood	0.3 pCi/L	10	0.1× under
320	Orange	0.3 pCi/L	6	0.1× under
321	Palm Desert	0.3 pCi/L	12	0.1× under
322	Signal Hill	0.3 pCi/L	17	0.1× under
323	La Palma	0.3 pCi/L	8	0.1× under
324	North Glendale	0.3 pCi/L	16	0.1× under
325	Petaluma	0.3 pCi/L	8	0.1× under
326	South San Francisco	0.3 pCi/L	8	0.1× under
327	Valencia	0.3 pCi/L	8	0.1× under
328	Lawndale	0.3 pCi/L	6	0.1× under
329	Arcadia	0.3 pCi/L	12	0.1× under
330	Cypress	0.3 pCi/L	6	0.1× under
331	Lompoc	0.3 pCi/L	6	0.1× under
332	Seal Beach	0.3 pCi/L	9	0.1× under
333	Bonita	0.3 pCi/L	9	0.1× under
334	Broadmoor	0.3 pCi/L	11	0.1× under
335	Newport Beach	0.3 pCi/L	7	0.1× under
336	Foster City	0.2 pCi/L	29	0.1× under
337	Santa Fe Springs	0.2 pCi/L	11	0.1× under
338	San Lorenzo	0.2 pCi/L	16	0.1× under

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